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            <div><h3 class="title">
                <a name="asio.reference.CancellationSlot"></a><a class="link" href="CancellationSlot.html"
                                                                 title="Cancellation slot requirements">Cancellation
                slot requirements</a>
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    <p>
        A type <code class="computeroutput"><span class="identifier">X</span></code> meets the <code
            class="computeroutput"><span class="identifier">CancellationSlot</span></code> requirements if it satisfies
        the requirements of <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>
        (C++Std [copyconstructible]) and <code class="computeroutput"><span
            class="identifier">Destructible</span></code>
        (C++Std [destructible]), as well as the additional requirements listed below.
    </p>
    <p>
        In the table below, <code class="computeroutput"><span class="identifier">x1</span></code> and
        <code class="computeroutput"><span class="identifier">x2</span></code> denote (possibly const)
        values of type <code class="computeroutput"><span class="identifier">X</span></code>, <code
            class="computeroutput"><span class="identifier">mx1</span></code> denotes an xvalue of type <code
            class="computeroutput"><span class="identifier">X</span></code>, <code class="computeroutput"><span
            class="identifier">H</span></code>
        denotes a type that satisfies <code class="computeroutput"><span
            class="identifier">CancellationHandler</span></code>,
        <code class="computeroutput"><span class="identifier">h</span></code> denotes an xvalue of type
        <code class="computeroutput"><span class="identifier">H</span></code>, and <code class="computeroutput"><span
            class="identifier">u0</span></code>
        to <code class="computeroutput"><span class="identifier">uN</span></code> denote identifiers.
    </p>
    <div class="table">
        <a name="asio.reference.CancellationSlot.t0"></a>
        <p class="title"><b>Table 8. CancellationSlot requirements</b></p>
        <div class="table-contents">
            <table class="table" summary="CancellationSlot requirements">
                <colgroup>
                    <col>
                    <col>
                    <col>
                </colgroup>
                <thead>
                <tr>
                    <th>
                        <p>
                            expression
                        </p>
                    </th>
                    <th>
                        <p>
                            type
                        </p>
                    </th>
                    <th>
                        <p>
                            assertion/note<br> pre/post-conditions
                        </p>
                    </th>
                </tr>
                </thead>
                <tbody>
                <tr>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">X</span> <span
                                    class="identifier">u</span><span class="special">(</span><span
                                    class="identifier">x1</span><span class="special">);</span></code>
                        </p>
                    </td>
                    <td>
                    </td>
                    <td>
                        <p>
                            Shall not exit via an exception.<br> <br> post: <code class="computeroutput"><span
                                class="identifier">u</span> <span class="special">==</span>
                            <span class="identifier">x1</span></code>.
                        </p>
                    </td>
                </tr>
                <tr>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">X</span> <span
                                    class="identifier">u</span><span class="special">(</span><span class="identifier">mx1</span><span
                                    class="special">);</span></code>
                        </p>
                    </td>
                    <td>
                    </td>
                    <td>
                        <p>
                            Shall not exit via an exception.<br> <br> post: <code class="computeroutput"><span
                                class="identifier">u</span></code> equals the prior value of
                            <code class="computeroutput"><span class="identifier">mx1</span></code>.
                        </p>
                    </td>
                </tr>
                <tr>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">x1</span> <span
                                    class="special">==</span>
                                <span class="identifier">x2</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="keyword">bool</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            Returns <code class="computeroutput"><span class="keyword">true</span></code> only
                            if <code class="computeroutput"><span class="identifier">x1</span></code> and <code
                                class="computeroutput"><span class="identifier">x2</span></code> can be interchanged
                            with identical
                            effects. <br> <code class="computeroutput"><span class="keyword">operator</span><span
                                class="special">==</span></code> shall be reflexive, symmetric,
                            and transitive, and shall not exit via an exception.
                        </p>
                    </td>
                </tr>
                <tr>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">x1</span> <span
                                    class="special">!=</span>
                                <span class="identifier">x2</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="keyword">bool</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            Same as <code class="computeroutput"><span class="special">!(</span><span
                                class="identifier">x1</span>
                            <span class="special">==</span> <span class="identifier">x2</span><span
                                    class="special">)</span></code>.
                        </p>
                    </td>
                </tr>
                <tr>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">x1</span><span
                                    class="special">.</span><span class="identifier">assign</span><span class="special">(</span><span
                                    class="identifier">h</span><span class="special">)</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">H</span><span
                                    class="special">&amp;</span></code>
                        </p>
                    </td>
                    <td>
                    </td>
                </tr>
                <tr>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">x1</span><span
                                    class="special">.</span><span class="identifier">emplace</span><span
                                    class="special">&lt;</span><span class="identifier">H</span><span class="special">&gt;(</span><span
                                    class="identifier">u0</span><span class="special">,</span>
                                <span class="special">...,</span> <span class="identifier">uN</span><span
                                        class="special">)</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            <code class="computeroutput"><span class="identifier">H</span><span
                                    class="special">&amp;</span></code>
                        </p>
                    </td>
                    <td>
                        <p>
                            Requires that <code class="computeroutput"><span
                                class="identifier">is_constructible</span><span class="special">&lt;</span><span
                                class="identifier">H</span><span class="special">,</span> <span
                                class="keyword">decltype</span><span class="special">(</span><span
                                class="identifier">u0</span><span class="special">),</span> <span
                                class="special">...,</span>
                            <span class="keyword">decltype</span><span class="special">(</span><span class="identifier">u0</span><span
                                    class="special">)&gt;::</span><span class="identifier">value</span></code> be true.
                        </p>
                    </td>
                </tr>
                </tbody>
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